1. Field of the Invention
The present invention relates to a display apparatus which outputs a pattern of the dot expression system and, more particularly, to a display apparatus which is constituted such as to send various pattern information in accordance with the attribute of the designated pattern.
2. Description of the Prior Art
Hitherto, a number of apparatuses which output pattern information of, for example, the dot expression format to form a desired pattern have been known. Such pattern information output apparatuses have an advantage such that when a number of kinds of patterns are formed as well, its output pattern can be easily changed. A CRT display apparatus of the dot refresh type, a wire-dot printer, a thermal printer, and the like are known as the pattern output apparatuses of the dot expression format.
In the above-mentioned CRT display apparatus of the dot refresh type, a code is predetermined for every pattern of a particular character or symbol, the pattern information (hereinafter, referred to as a font) of the particular character or symbol is read out in accordance with the code, the font read out is temporarily stored in a video RAM, such pattern information is repeatedly read out at a high speed, and thereby displaying it on the CRT display.
In the case where an underline is added to a character or a character is displayed as a thick character (hereinafter, referred to as a bold character), to emphasize the character by use of the foregoing CRT display apparatus of the dot refresh type, printer or the like, in order to avoid an increase in capacity of a memory for storing the fonts, the underlined fonts and bold fonts are not individually stored, but the pattern information read out from the memory is subjected to a predetermined image process, thereby adding a desired underline to the pattern information or changing it to a bold character (patterns processed by said predetermined image process are hereinafter called "ornamented patterns"). In addition, in the case of inverting the contrast of a character as well, a predetermined image process is likewise performed. The above-mentioned underline, bold, inverting display, etc. are generally called "attribute" of a character.
As an example, a conventional technology in the case of displaying the "bold" character as one of the attributes of a character will now be described. In this case, the font read out from the memory is shifted to the left or right by only one dot, OR of the font derived and the font before shifting is obtained, the result of the arithmetic logic operation is transferred to the video RAM, and thereby realizing the bold display as a bold character.
However, the pattern information output apparatuses based on the above-mentioned systems have the following drawbacks.
(1) As shown in FIG. 2, in the case of bold displaying the minus symbol ("-") or the like, the font is merely laterally shifted by one dot, so that it is difficult to discriminate whether such a symbol is displayed as a bold character or not.
(2) In the case of bold displaying a small letter "m" (or "w" or the like) using a display device with a low resolution, as shown in FIG. 3, the dots are displayed at the adjacent positions, so that the letter itself will not be able to be discriminated.
Further, in a sentence processing apparatus using such a display apparatus, there are the cases of displaying special functions such as superscript (a character written immediately above or above and to the right or left of another character), subscript (a character written immediately below or below and to the right or left of another character), stop position (temporary print interruption point to exchange a daisy wheel (part for printing) or the like during the printing), change start position of a line space, and the like. For example, in the case of superscript, hitherto, an upward arrow (.uparw.) is overlapped on a character and both the arrow and the character are together displayed. However, there are drawbacks such that it is very difficult for the operator to see such overlapped character and also it is impossible to discriminate the original character of the overlapped character. In addition, there is a risk such that such overlapped character reduces the use efficiency of a document processing apparatus.